Comparison of UV and UV-LED activated sodium percarbonate for the degradation of O-desmethylvenlafaxine

As an active metabolite of venlafaxine and emerging antidepressant,Odesmethylvenlafaxine(ODVEN) was widely detected in different water bodies,which caused potential harm to human health and environmental safety.In this study,the comparative work on the ODVEN degradation by UV(254 nm) and UV-LED(275 nm) activated sodium percarbonate(SPC) systems was systematically performed.The higher removal rate of ODVEN can be achieved under UV-LED direct photolysis(14.99%) than UV direct photolysis(4.57%) due to the higher values of photolysis coefficient at the wavelength 275nm.Significant synergistic effects were observed in the UV/SPC(80.38%) and UV-LED/SPC(53.57%) systems and the former exhibited better performance for the elimination of ODVEN.The degradation of ODVEN all followed the pseudo-first-order kinetics well in these processes,and the pseudo-first-order rate constant(kobs) increased with increasing SPC concentration.Radicals quenching experiments demonstrated that both ·OH and CO_(3)·-were involved in the degradation of ODVEN and the second-order rate constant of ODVEN with CO_(3)·-(1.58 × 10^(8)(mol/L)-1sec-1) was reported for the first time based on competitive kinetic method.The introduction of HA,Cl-,NO_(3)-and HCO_(3)-inhibited the ODVEN degradation to varying degrees in the both processes.According to quantum chemical calculation,radical addition at the ortho-position of the phenolic hydroxyl group was confirmed to be the main reaction pathways for the oxidation of ODVEN by·OH.In addition,the oxidation of ODVEN may involve the demethylation,H-abstraction,OH^(-)addition and C-N bond cleavage.Eventually,the UV-LED/SPC process was considered to be more cost-effective compared to the UV/SPC process,although the UV/SPC process possessed a higher removal rate of ODVEN.

Enhanced reductive degradation of carbon tetrachloride by carbon dioxide radical anion-based sodium percarbonate/ Fe（ll）/formic acid system in aqueous solution

The performance of sodium percarbonate （SPC） activated with ferrous ion （Fe（Ⅱ） with the addition of formic acid （FA） to stimulate the degradation of carbon tetrachloride （CT） was investigated. Results showed that CT could be entirely reduced within 15 min in the system at a variety of SPC/Fe（Ⅱ）/FA/CT molar ratios in experimental level. Scavenging tests indicated that carbon dioxide radical anion （CO2-） was the dominant reactive oxygen species responsible for CT degradation. CT degradation rate, to a large extent, increased with increasing dosages of chemical agents and the optimal molar ratio of SPC/Fe（Ⅱ）/FAJCT was set as 60/60/60/1. The initial concentration of CT can hardly affect the CT removal, while CT degradation was favorable in the pH range of 3.0-9.0, but apparently inhibited at pH 12. C1- and HCO3 of high concentration showed negative impact on CT removal. Cl- released from CT was detected and the results confirmed nearly complete mineralization ofCT. CT degradation was proposed by reductive C-C1 bond splitting. This study demonstrated that SPC activated with Fe（Ⅱ） with the addition of FA may be promising technique for CT remediation in contaminated groundwater.

Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate(SPC)and peroxymonocarbonate(PMC)have been widely used in modified Fenton reactions because of their multiple superior features,such as a wide pH range and environmental friendliness.This broad review is intended to provide the fundamental information,status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades.Both SPC and PMC can directly decompose various pollutants.The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC.The most commonly used catalysts for SPC activation are iron compounds while cobalt composi-tions are applied to activate PMC in homogenous and heterogeneous catalytical systems.The generation and participation of hydroxyl,superoxide and/or carbonate radicals are involved in the activated SPC and PMC system.The reductive radicals,such as carbon dioxide and hydroxyethyl radicals,can be generated when formic acid or methanol is added in the Fe(II)/SPC system,which can reduce target contaminants.SPC can also be activated by energy,tetraacetylethylenediamine,ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition.The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment.The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.